Short-term Borrowings and Short-term Bank Lines of Credit (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Short-term Debt [Line Items]
Amount of outstanding cash borrowings	$ 9,000,000	$ 12,000,000
Commercial paper outstanding	108,200,000	530,100,000
Parent Company [Member]
Short-term Debt [Line Items]
Amount of outstanding cash borrowings	9,000,000	12,000,000
Parent Company [Member] | Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Amount of revolving credit facility	200,000,000
Revolving credit facility expiration date	Oct. 01, 2018
Maximum borrowing capacity with transfer of unused commitments	400,000,000
Covenant term - amount considered in default	50,000,000
Covenant Term Ratio of Consolidated Indebtedness to Consolidated Capitalization Ratio, Maximum	0.65
Line of Credit Facility, Covenant Compliance	in compliance
Amount of outstanding cash borrowings	9,000,000	12,000,000
Weighted-average interest rate from outstanding borrowings	1.94%	2.00%
Amount of letters of credit outstanding	0	1,800,000
Kansas City Power and Light Company [Member]
Short-term Debt [Line Items]
Commercial paper outstanding	93,200,000	361,000,000
Weighted-average interest rate from outstanding borrowings	0.29%	0.48%
Kansas City Power and Light Company [Member] | Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Amount of revolving credit facility	600,000,000
Revolving credit facility expiration date	Oct. 01, 2018
Maximum transfer of unused commitments	200,000,000
Covenant term - amount considered in default	50,000,000
Covenant Term Ratio of Consolidated Indebtedness to Consolidated Capitalization Ratio, Maximum	0.65
Line of Credit Facility, Covenant Compliance	in compliance
Amount of outstanding cash borrowings	0	0
Amount of letters of credit outstanding	3,800,000	13,900,000
KCPL Greater Missouri Operations [Member]
Short-term Debt [Line Items]
Commercial paper outstanding	15,000,000	169,100,000
Weighted-average interest rate from outstanding borrowings	0.66%	0.94%
KCPL Greater Missouri Operations [Member] | Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Amount of revolving credit facility	450,000,000
Revolving credit facility expiration date	Oct. 01, 2018
Maximum transfer of unused commitments	200,000,000
Covenant term - amount considered in default	50,000,000
Covenant Term Ratio of Consolidated Indebtedness to Consolidated Capitalization Ratio, Maximum	0.65
Line of Credit Facility, Covenant Compliance	in compliance
Amount of outstanding cash borrowings	0	0
Amount of letters of credit outstanding	$ 16,400,000	$ 15,100,000